L4945

® L4945 5V VERY LOW DROP VOLTAGE REGULATOR 5V ± 4% PRECISE OUTPUT VOLTAGE OVER FULL TEMPERATURE RANGE (– 40 / 125 °C) VERY LOW VOLTAGE DROP (0.75Vmax) OVER FULL TEMPERATURE RANGE OUTPUT CURRENT UP TO 500mA OVERVOLTAGE AND REVERSE VOLTAGE PROTECTIONS REVERSE VOLTAGE PROTECTION SHORT CIRCUIT PROTECTION AND THERMAL SHUT-DOWN (with hysteresis) LOW START UP CURRENT DESCRIPTION The L4945 is a monolithic integrated circuit in Versawatt package specially designed to provide a stabilized supply voltage for automotive and industrial electronic systems. Thanks to their very low voltage drop, in automotive applications the devices can work correctly even during the crankBLOCK DIAGRAM TO220 ORDERING NUMBER: L4945 ing phase, when the battery voltage could fall as low as 6V. Furthermore, they incorporate a complete range of protection circuits against the dangerous overvoltages always present on the battery rail of the car. This is advanced information on a new product now in development or undergoing evaluation. Details are subject to change without notice. March 1999 1/6 L4945 ABSOLUTE MAXIMUM RATINGS Symbol Vi Parameter DC Input Voltage DC Reverse Input Voltage Transient Input Overvoltages : Load Dump : 5ms ≤ trise ≤ 10ms τf Fall Time Constant = 100ms RSOURCE ≥ 0.5Ω Field Decay : 5ms ≤ tfall ≤ 10ms, RSOURCE ≥ 10Ω τr Rise Time Constant = 33ms Low Energy Spike : trise = 1µs, tfall = 500µs, RSOURCE ≥ 10Ω fr Repetition Frequency = 5Hz Junction Temperature Range Operating Temperature Range Storage Temperature Range Value 35 – 18 80 Unit V V V – 80 ± 100 V V TJ TOP Tstg – 40 to 150 – 40 to 125 – 55 to 150 °C °C °C Note: The circuit is ESD protected according to MIL-STD-883C. PIN CONNECTION (Top view) THERMAL DATA Symbol R th j-case Parameter Thermal Resistance Junction-case Max Value 3 Unit °C/W 2/6 L4945 TEST CIRCUIT ELECTRICAL CHARACTERISTICS (refer to the test circuit, Vi = 14. 4V, Co = 47µF, ESR < 10Ω, Rp = 1KΩ, RL = 1KΩ, –40°C ≤ TJ ≤ 125°C, unless otherwise specified) Symbol Vo Parameter Output Voltage Test Conditions Io = 0mA to 500mA Over Full T Range Tj = 25°C Vi ∆V o ∆V o Vi –Vo Iq ∆ Vo Operating Input Voltage Line Regulation Load Regulation Dropout Voltage Quiescent Current Io = 0mA to (*) 500mA Vi = 6V to 26V ; Io = 5mA Io = 5mA to 500mA Io = 500mA, TJ = 25°C Over Full T Range Io = 0mA, TJ = 25°C Io = 0mA Over Full T Io = 500mA Over Full T Min. 4.80 4.90 6 2 15 0.40 5 6.5 110 – 0.5 Io = 350mA ; f = 120Hz C o = 100µF ; Vi = 12V ± 5Vpp 50 60 Typ. 5.00 5.00 Max. 5.20 5.10 26 10 60 0.55 0.75 10 13 180 Unit V V V mV mV V V mA mA mA mV/°C dB T SVR Temperature Output Voltage Drift Supply Volt. Rej. Isc Output Short Circuit Current 0.50 0.80 1.50 A (*) For a DC voltage 26 < Vi < 37V the device is not operating F UNCTIONAL DESCRIPTION The block diagram shows the basic structure of the devices : the reference, the error amplifier, the driver, the power PNP, the protection and reset functions. The power stage is a Lateral PNP transistor which allows a very low dropout voltage (typ. 400mV at TJ = 25°C, max. 750mV over the full temperature range @ IO = 500mA). The typical curve of the dropout voltage as a function of the junction temperature is shown in Fig. 1 : that is the worst case, where IO = 500mA. The current consumption of the devices (quiescent current) are maximum 10mA - over full T - when no load current is required. The internal antisaturation circuit allows a drastic reduction in the current peak which takes place during the start up. The three gain stages (operational amplifier, driver and power PNP) require the external capacitor (Comin = 20µF) to guarantee the global stability of the system. Load dump and field decay protections (± 80V, t = 300ms), reverse voltage (– 18V) and short circuit protection, thermal shutdown are the main features that make the devices specially suitable for applications in the automotive enviroment. 3/6 L4945 Figure 1: Typical Dropout Voltage vs. Tj (Io = 500mA). ous poles present in the loop. To avoid this instability dominant pole compensation is used to reduce phase shift due to other poles at the unity gain frequency. The lower the frequency of these others poles at the unity gain frequency. The lower the frequency of these other poles, the greater must be capacitor esed to create the dominant pole for the same DC gain. Where the output transistor is a lateral PNP type there is a pole in the regulation loop at a frequencybtoo low to be compensated by a capacitor which can be integrated. An external compensation is therefore necessary so a very high value capacitor must be connected from the output to ground. The paeassitic equivalent series resistance of the capacitor used adds a zero to the regulation loop. This zero may compromise the stability of the system since its effect tends to cancel the effect of the pole added. In regulators this ESR must be less than 3Ω and the minimum capacitor value is 47µF. EXTERNAL COMPENSATION Since the purpose of a voltage regulator is to supply and load variations, the open loop gain of the regulators must be very high at low frequencies. This may cause instability as a result of the vari- 4/6 L4945 mm MIN. A C D E F F1 F2 G G1 H2 L2 L4 L5 L6 L7 L9 M Dia 3.75 13.0 2.65 15.25 6.20 3.50 2.6 3.85 0.147 4.40 1.23 2.40 0.49 0.61 1.14 1.14 4.95 2.40 10.0 16.4 14.0 2.95 15.75 6.60 3.93 0.511 0.104 0.600 0.244 0.137 0.102 0.151 TYP. MAX. 4.60 1.32 2.72 0.70 0.88 1.70 1.70 5.15 2.70 10.4 MIN. 0.173 0.048 0.094 0.019 0.024 0.044 0.044 0.194 0.094 0.393 0.645 0.551 0.116 0.620 0.260 0.154 inch TYP. MAX. 0.181 0.051 0.107 0.027 0.034 0.067 0.067 0.203 0.106 0.409 DIM. OUTLINE AND MECHANICAL DATA Versawatt (TO220) M TO220MEC 5/6 L4945 I nformation furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics © 1999 STMicroelectronics – Printed in Italy – All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - Canada - China - France - Germany - Italy - Japan - Korea - Malaysia - Malta - Mexico - Morocco - The Netherlands Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A. http://www.st.com 6/6